The invention relates to an electro-acoustic transducer comprising a transducer plate which is arranged in a housing and by which the space within the housing is divided into a front chamber and a rear chamber. A fitting which closes off the front chamber is also provided together with at least one Helmholtz resonator arranged in the rear chamber and which serves to attenuate rises in resonance.
In electro-acoustic transducers used in telephone technology, the rise in resonance caused by the mass and the springiness of the diaphragm is compensated in a known manner by means of a Helmholtz absorption resonator attached to the rear chamber of the diaphragm. For this purpose the mass, springiness and friction of the air are established by geometrically constructing the Helmholtz resonator in the form of a collar to which an attenuating material such as silk, wire latticework, or sintered metal is subsequently applied. The flow resistance of the attenuating material is however subject to relatively high tolerances which are further increased by the application of the attenuating material to the collar, for example as a result of an adhesive process, as a result of which disadvantageous deviations can occur in high volume production. A further disadvantage consists in the relatively high costs for materials, assembly and checking.
In another known structure (German OS No. 2 322 475, incorporated herein by reference), the mass and friction of the air is compensated in annular gaps which possess a width of approximately 100 to 150 .mu.m and which are relatively long (a few mm), and which are formed by two synthetic die cast components which project into one another. Here cylindrical pins of a transducer housing project into holes distributed uniformly over the periphery of a partition wall, where the pins possess a somewhat smaller diameter than the holes. The disadvantage of such a solution consists in the very high degree of accuracy demanded for the two die-cast components.